Bipolar plate of fuel cell

ABSTRACT

In a bipolar plate of a fuel cell including a plate having a certain area and thickness; inflow and outflow buffer grooves respectively formed at both sides of the plate so as to have a certain area and depth; plural channels for connecting the inflow buffer groove and the outflow buffer groove; plural buffer protrusions formed in the inflow and outflow buffer grooves so as to have a certain height; an inflow path formed on the plate so as to be connected to the inflow buffer groove; and an outflow path formed on the plate so as to be connected to the outflow buffer groove, it is possible to uniformize flux distribution and reduce flow resistance of fuel and air respectively flowing into a fuel electrode and an air electrode of a fuel cell.

TECHNICAL FIELD

The present invention relates to a fuel cell, and in particular to abipolar plate of a fuel cell capable of uniformizing flux distributionand reducing flow resistance of fuel and air respectively flowing into afuel electrode (anode) and an air electrode (cathode) of a fuel cell.

BACKGROUND ART

A fuel cell is generally environment-friendly energy, and it has beendeveloped in order to substitute for the conventional fossil energy. Asdepicted in FIG. 1, the fuel cell includes a stack to be combined withat least one unit cell 11 in which electron-chemical reaction occurs; afuel supply pipe 20 connected to the stack 10 so as to supply fuel; anair supply pipe 30 connected to the stack 10 so as to supply air; anddischarge pipes 40, 50 for discharging by-products of fuel and airpassing the reaction respectively. The unit cell 11 includes a fuelelectrode (anode) (not shown) in which fuel flows; and an air electrode(cathode) (not shown) in which air flows.

The operation of the fuel cell will be described.

First, fuel and air are supplied to the fuel electrode and the airelectrode of the stack 10 through the fuel supply pipe 20 and the airsupply pipe 30 respectively. Fuel supplied to the fuel electrode isionized into positive ions and electrons (e-) through electrochemicaloxidation reaction in the fuel electrode, the ionized positive ions aremoved to the air electrode through an electrolyte layer, and theelectrons are moved to the fuel electrode. The positive ions moved tothe air electrode perform electrochemical reduction reaction with airsupplied to the air electrode and generate by-products such as reactionheat and water, etc. In the process, by the movement of the electrons,electric energy is generated. The fuel through the reaction in the fuelelectrode, and water and additional by-products generated in the airelectrode are respectively discharged through the discharge lines 40,50.

The fuel cell can be classified into various types according to kinds ofelectrolyte and fuel, etc. used therein.

In the meantime, as depicted in FIG. 2, the unit cell 11 constructingthe stack 10 includes two bipolar plates 100 having an open channel 101in which air or fuel flows; and a M.E.A (membrane electrode assembly)110 arranged between the two bipolar plates 100 so as to have a certainthickness and area. The two bipolar plates 100 and the M.E.A 110arranged therebetween are combined with each other by additionalcombining means 120, 121. A channel formed by a channel 101 of thebipolar plate 100 and a side of the M.E.A 110 constructs a fuelelectrode, and oxidation reaction occurs while fuel flows through thechannel of the fuel electrode. And, a channel formed by a channel 101 ofthe other bipolar plate 100 and the other side of the M.E.A 110constructs an air electrode, and reduction reaction occurs while airflows through the channel of the air electrode.

A shape of the bipolar plate 100, in particular, a shape of the channel101 affects contact resistance generated in flowing of fuel and air andflux distribution, etc., and contact resistance and flux distributionaffect power efficiency. And, the bipolar plates 100 have a certainshape appropriate to processing facilitation and mass production.

As depicted in FIG. 3, in the conventional first bipolar plate, throughholes 131, 132, 133, 134 are respectively formed at each edge of theplate 130 having a certain thickness and a rectangular shape. Among thefour through holes, the diagonally arranged two through holes 131, 133are fuel paths, and the diagonally arranged two through holes 132, 134are air paths. Hexagonal channel 135 in which a fluid flows isrespectively formed at both sides of the plate 130, and plural straightchannels 136 are horizontally formed along the whole internal area ofthe hexagonal channel 135. And, the hexagonal channel 135 formed at theside of the plate 130 and the plural straight connection channels 136are connected to the diagonally arranged two through holes 131, 133through plural straight channels 137. And, the hexagonal channel 135formed at the other side of the plate 130 and the plural straightchannels 136 are connected to the diagonally arranged two through holes132, 134 through plural straight connection channels 137. In moredetail, in the plate 130, fuel flows on the side, and air flows on theother side.

FIG. 3 is a plane view illustrating a side of the conventional bipolarplate.

The operation of the conventional bipolar plate will be described. Fuelor air flows into the through holes 131, 132, the fuel or air flows intothe hexagonal channel 135 and the plural straight channels 136 throughthe connection channels 137, and it flows into the connection channelsat the other side. The fuel or air flowing into the connection channels137 are discharged through the through holes 133, 134 at the other side.

In the meantime, in another structure of the conventional second bipolarplate, as depicted in FIG. 4, through holes 141, 142, 143, 144 arerespectively formed at edges of the plate 140 having a certain thicknessand a rectangular shape. And, curved plural channels 145 are formed on aside of the plate 140 so as to connect the diagonally arranged twothrough holes 141, 143. And, curved plural channels 145 are formed onthe other side of the plate 140 so as to connect the diagonally arrangedtwo through holes 142, 144.

The operation of the second bipolar plate will be described. Fuel andair respectively flow into the through holes 141, 142, fuel or airrespectively flowing into the through holes 141, 142 passes the pluralchannels 145 and is discharged through the other through holes 143, 144.

However, in the conventional first bipolar plate, because the number ofthe connection channels 137 for connecting the through holes 131, 132,133, 134, the hexagonal channel 135 and the straight channels 136 isvery little in comparison with the number of the straight channels 136formed in the hexagonal channel, flux distribution of a fluid flowinginto the through holes 131, 132 is not good, and it is inappropriate tousing the conventional first bipolar plate in flowing of great amount offluid. In the meantime, in the conventional second bipolar plate,because the channels 145 of fuel and air are formed as a curved shape,flow resistance is increased in flowing of fuel and air, and accordinglypressure loss for flowing the fluid is increased.

TECHNICAL GIST OF THE PRESENT INVENTION

In order to solve the above-mentioned problems, it is an object of thepresent invention to provide a bipolar plate of a fuel cell capable ofuniformizing flux distribution and reducing flow resistance of fuel andair respectively flowing into a fuel electrode and an air electrode.

In order to achieve the above-mentioned object, a bipolar plate of afuel cell in accordance with the present invention includes a platehaving a certain area and thickness; inflow and outflow buffer groovesrespectively formed at both sides of the plate so as to have a certainarea and depth; plural channels for connecting the inflow buffer grooveand the outflow buffer groove; an inflow path formed on the plate so asto be connected to the inflow buffer groove; and an outflow path formedon the plate so as to be connected to the outflow buffer groove.

In addition, a bipolar plate of a fuel cell in accordance with thepresent invention includes a plate having a certain area and thickness;inflow and outflow buffer grooves respectively formed at both sides ofthe plate so as to have a certain area and depth; plural channels forconnecting the inflow buffer groove and the outflow buffer groove;plural buffer protrusions formed in the inflow and outflow buffergrooves so as to have a certain height; an inflow path formed on theplate so as to be connected to the inflow buffer groove; and an outflowpath formed on the plate so as to be connected to the outflow buffergroove.

BRIEF DESCRIPTION OF DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the invention and are incorporated in and constitute apart of this specification, illustrate embodiments of the invention andtogether with the description serve to explain the principles of theinvention.

In the drawings:

FIG. 1 shows the conventional fuel cell system;

FIG. 2 is an exploded-perspective view illustrating a stack of theconventional fuel cell;

FIG. 3 is a plane view illustrating an example of a bipolar plate of theconventional fuel cell;

FIG. 4 is a plane view illustrating another example of a bipolar plateof the conventional fuel cell;

FIG. 5 is a plane view illustrating a first embodiment of a bipolarplate of a fuel cell in accordance with the present invention;

FIG. 6 is a sectional view taken along a line A-B in FIG. 5;

FIGS. 7 and 8 are plane views respectively illustrating channels of thebipolar plate of the fuel cell in accordance with the first embodimentof the present invention;

FIG. 9 is a plane view illustrating distribution means of the bipolarplate of the fuel cell in accordance with the first embodiment of thepresent invention;

FIG. 10 is a plane view illustrating a second embodiment of a bipolarplate of a fuel cell in accordance with the present invention;

FIG. 11 is a sectional view taken along a line C-D in FIG. 10;

FIGS. 12 and 13 are plane views respectively illustrating modificationsof buffer protrusions of the bipolar plate of the fuel cell inaccordance with the second embodiment of the present invention;

FIGS. 14 and 15 are plane views respectively illustrating other examplesof channels of the bipolar plate of the fuel cell in accordance with thesecond embodiment of the present invention;

FIG. 16 is a plane view illustrating distribution means of the bipolarplate of the fuel cell in accordance with the second embodiment of thepresent invention;

FIG. 17 is an exploded-perspective view illustrating a stack of thebipolar plate of the fuel cell in accordance with the second embodimentof the present invention;

FIG. 18 is a plane view illustrating an operational state of the bipolarplate of the fuel cell in accordance with the first embodiment of thepresent invention; and

FIG. 19 is a plane view illustrating an operational state of the bipolarplate of the fuel cell in accordance with the second embodiment of thepresent invention.

DETAILED DESCRIPTION OF THE INVENTION

Hereinafter, the preferred embodiments of a bipolar plate of a fuel cellin accordance with the present invention will be described withreference to accompanying drawings.

First, a first embodiment of a bipolar plate of a fuel cell inaccordance with the present invention will be described.

FIG. 5 is a plane view illustrating a first embodiment of a bipolarplate of a fuel cell in accordance with the present invention, and FIG.6 is a sectional view taken along a line A-B in FIG. 5.

As depicted in FIGS. 5 and 6, the bipolar plate of the fuel cell inaccordance with the present invention includes a plate 150 having acertain area and thickness; inflow and outflow buffer grooves 151, 152respectively formed at both sides of the plate 150 so as to have acertain area and depth; plural channels 153 for connecting the inflowbuffer groove 151 and the outflow buffer groove 152; an inflow path 154formed on the plate 150 so as to be connected to the inflow buffergroove 151; and an outflow path 155 formed on the plate 150 so as to beconnected to the outflow buffer groove 152.

The plate 150 is formed as a rectangular shape and has a uniformthickness. The inflow buffer groove 151 is formed as a rectangular shapehaving a certain width and length, and it has the uniform depth. Widthand length of the outflow buffer groove 152 are the same with those ofthe inflow buffer groove 151, and the outflow buffer groove 152 has theuniform depth. The inflow buffer groove 151 and the outflow buffergroove 152 are arranged on the same line and have the same depth.

The inflow buffer groove 151 and the outflow buffer groove 152 can haveother shapes besides the rectangular shape and have different depth.

And, plural channels 153 are formed between the inflow buffer groove 151and the outflow buffer groove 152 in order to connect them. The channels153 are straight and have the uniform width. In addition, the channels153 have the same depth with the inflow buffer groove 151 and theoutflow buffer groove 152.

In the meantime, as depicted in FIG. 7, in another example of thechannels 153, channel width is increased gradually from the channel 153arranged on the middle to the channel 153 arranged on the edge. In moredetail, in order to distribute the fluid in the inflow buffer groove 151to the channels 153 evenly, width of the middle channel is narrower,width of the edge channel is wider, and width of each channel islinearly increased.

As depicted in FIG. 8, in yet another example of the channels 153, thechannels 153 have the same width, and a buffer portion 156 is formed atthe inlet side of each channel 153 so as to reduce a width of the inlet.The buffer portion 156 is a protrusion extended-projected from bothwalls constructing the channel 153. The buffer portion 156 is fordistributing the fluid flowing into the inflow buffer groove 151 to thechannels 153 uniformly.

The length of the inflow buffer groove 151 and the outflow buffer groove152 is not less than ⅕ of the length of the channel 153.

The inflow buffer channel 154 is formed at a side of the plate 150 so asto be arranged on the length line of the channels 153. The inflow path154 is constructed as at least one through hole.

The outflow path 155 is formed at a side of the plate 150 so as to bearranged on the length line of the channels 153 and on the opposite sideof the inflow path 154. The outflow path 155 is formed as at leastthrough hole.

And, as depicted in FIG. 9, a distribution means (R) for giving flowresistance to the fluid flowing into the inflow path 154 can be arrangedin the inflow path 154.

The distribution means (R) is formed as a shape having an areacorresponded to the section of the inflow path 154 and a certainthickness and is made of a porous material. The distribution means (R)uniformizes distribution of the fluid flowing into each unit cell byinducing flow resistance of the fluid flowing into the inflow path 154.

When the bipolar plate of the fuel cell in accordance with the firstembodiment of the present invention constructs a unit cell or isarranged on both sides of a stack, the inflow buffer groove 151, theoutflow buffer groove 152 and the plural channels 153, etc. are formedonly on one side of the plate 150.

Next, a bipolar plate of a fuel cell in accordance with a secondembodiment of the present invention will be described.

FIG. 10 is a plane view illustrating a second embodiment of a bipolarplate of a fuel cell in accordance with the present invention, and FIG.11 is a sectional view taken along a line C-D in FIG. 10.

As depicted in FIGS. 10 and 11, the bipolar plate of the fuel cell inaccordance with the second embodiment of the present invention includesa plate 160 having a certain area and thickness; inflow and outflowbuffer grooves 161, 162 respectively formed at both sides of the plate160 so as to have a certain area and depth; plural channels 163 forconnecting the inflow buffer groove 161 and the outflow buffer groove162; plural buffer protrusions 164 formed in the inflow and outflowbuffer grooves 161, 162 so as to have a certain height; an inflow path165 formed on the plate 160 so as to be connected to the inflow buffergroove 161; and an outflow path 166 formed on the plate 160 so as to beconnected to the outflow buffer groove 162.

The plate 160 is formed as a rectangular shape and has a uniformthickness. The inflow buffer groove 161 is formed as a rectangular shapehaving a certain width and length, and it has the uniform depth. Widthand length of the outflow buffer groove 162 are the same with those ofthe inflow buffer groove 161, and the outflow buffer groove 152 has theuniform depth. The inflow buffer groove 161 and the outflow buffergroove 162 are arranged on the same line and have the same depth.

Plural channels 163 are formed between the inflow buffer groove 161 andthe outflow buffer groove 162 in order to connect them. The channels 163are straight and have the same depth with the inflow and outflow buffergrooves 161, 162. A length of the inflow and outflow buffer grooves 161,162 is not less than ⅕ of the length of the channel 163.

The buffer protrusions 164 are linearly formed between the channels 163.

As depicted in FIG. 12, the buffer protrusions 164 having a modifiedshape are linearly arranged on the channels 163.

The buffer protrusions 164 have the same height. The height of thebuffer protrusion is the same with the depth of the inflow buffer groove161 or the outflow buffer groove 162.

A section of the buffer protrusion 164 is rectangular. A section of thebuffer protrusion 164 can be other shapes besides a rectangular shape.

As depicted in FIG. 13, as a modified form, the buffer protrusions 164are irregularly arranged.

The inflow and outflow buffer grooves 161, 162 can have other shapesbesides a rectangular shape and can have different depth.

In the meantime, as depicted in FIG. 14, in another example of thechannels 163, channel width is increased gradually from the channel 163arranged on the middle to the channel 163 arranged on the edge. In moredetail, in order to distribute the fluid in the inflow buffer groove 161to the channels 163 uniformly, width of the middle channel is narrower,width of the edge channel is wider, and width of each channel islinearly increased.

As depicted in FIG. 15, in yet another example of the channels 163, thechannels 163 have the same width, and a buffer portion 167 is formed atthe inlet side of each channel 163 so as to reduce a width of the inlet.The buffer portion 167 is a protrusion extended-projected from bothwalls constructing the channel 163. The buffer portion 167 is fordistributing the fluid flowing into the inflow buffer groove 161 to thechannels 163 uniformly.

The inflow buffer channel 165 is formed at a side of the plate 160 so asto be arranged on the length line of the channels 163. The inflow path165 is constructed as at least one through hole.

The outflow path 166 is formed at a side of the plate 160 so as to bearranged on the length line of the channels 163 and on the opposite sideof the inflow path 165. The outflow path 166 is formed as at leastthrough hole.

And, as depicted in FIG. 16, a distribution means (R) for giving flowresistance to the fluid flowing into the inflow path 165 can be arrangedin the inflow path 165.

The distribution means (R) is formed as a shape having an areacorresponded to the section of the inflow path 165 and a certainthickness and is made of a porous material. The distribution means (R)uniformizes distribution of the fluid flowing into each unit cell byinducing flow resistance of the fluid flowing into the inflow path 165.

When the bipolar plate of the fuel cell in accordance with the secondembodiment of the present invention constructs a unit cell or isarranged on both sides of a stack, the inflow buffer groove 161, theoutflow buffer groove 162, the buffer protrusions 164 and the pluralchannels 163, etc. are formed only on one side of the plate 160.

Hereinafter, operational advantages of the bipolar plate of the fuelcell in accordance with the present invention will be described.

First, in the bipolar plate of the fuel cell in accordance with thepresent invention, bipolar plates construct a stack of a fuel cell. Inmore detail, as depicted in FIG. 17, a M.E.A (M) is arranged between thebipolar plates (BP), they are combined with each other by a combiningmeans (not shown), and accordingly a stack of a fuel cell isconstructed. Herein, the fuel channel in which fuel flows is formed bythe inflow buffer groove 151, the channels 153 and the outflow buffergroove 152, etc formed on one side of the bipolar plate (BP) and oneside of the M.E.A (M). And, the air channel in which air flow is formedby the inflow buffer groove 151 formed on the other side of the M.E.A(M) and the inflow buffer groove 151, the channels 153 and the outflowbuffer groove 152, etc formed on one side of the other bipolar plate(BP) facing the bipolar plate (BP).

In the structure, when the fuel flows into the inflow path 154 of thebipolar plate (BP), as depicted in FIG. 18, the flow in the inflow path154 flows into the inflow buffer groove 151. And, the fuel in the inflowbuffer groove 151 spreads all over the inflow buffer groove 151 andflows into the channels 153. The fuel in the channels 153 flows into theoutflow buffer groove 152 and is discharged to the outside through theoutflow path 155. In that process, because the fuel from the inflow path154 flows into the channels 153 after passing the inflow buffer groove151, flux is evenly distributed to the all channels 153, and accordinglyflowing can be smooth. In addition, the fuel flowing through thechannels 153 is gathered in the outflow buffer groove 152 and isdischarged to the outside through the outflow path 155, and accordinglyflowing of the fuel can be smooth.

In addition, air flows by passing the above-mentioned process.

In the bipolar plate of the fuel cell in accordance with the secondembodiment of the present invention, as depicted in FIG. 19, the fuelflows into the inflow buffer groove 161 through the inflow path 165. Thefuel in the inflow buffer groove 161 spreads generally by the inflowbuffer groove 161 and the buffer protrusions 164 arranged in the inflowbuffer groove 161 and is distributed evenly to the channels 163. Thefuel flowing through the channels 163 is gathered in the outflow buffergroove 162 and is discharged to the outside through the outflow path166. In the structure, by the buffer protrusions 164, the fuel isdistributed to the channels 163 more evenly, area contacted-supportedwith the M.E.A (M) between the bipolar plates (BP) is broadened, andaccordingly deformation of the M.E.A (M) can be minimized.

In the meantime, in the bipolar plate of the fuel cell in accordancewith the present invention, by forming the channels 153, 163 linearly,processing can be easier, and processing methods can be diversified.

INDUSTRIAL APPLICABILITY

As described-above, in the bipolar plate of the fuel cell in accordancewith the present invention, by distributing evenly flux of fuel and airrespectively flowing in the fuel electrode and the air electrode,effective area of oxidation reaction and reduction reaction isincreased, and power efficiency can be improved. By reducing flowresistance of fuel and air, pumping power for flowing fuel and air isreduced, and efficiency of a fuel cell can be improved. In addition, byfacilitating processing and diversifying processing methods, aproduction cost can be reduced.

1. A bipolar plate of a fuel cell, comprising: a plate having a certainarea and thickness; inflow and outflow buffer grooves respectivelyformed at both sides of the plate so as to have a certain area anddepth; plural channels for connecting the inflow buffer groove and theoutflow buffer groove; an inflow path formed on the plate so as to beconnected to the inflow buffer groove; and an outflow path formed on theplate so as to be connected to the outflow buffer groove.
 2. The bipolarplate of claim 1, wherein the channels are linearly formed.
 3. Thebipolar plate of claim 2, wherein channel width is increased graduallyfrom a channel arranged on the middle to a channel arranged on the edge.4. The bipolar plate of claim 2, wherein width of the channels isuniform, and a projected buffer portion is formed at an inlet side ofeach channel so as to reduce a width of the inlet.
 5. The bipolar plateof claim 1, wherein the inflow path and the outflow path is respectivelyconstructed as at least one through hole.
 6. The bipolar plate of claim1, wherein the inflow path and the outflow path are formed at a side ofthe plate.
 7. The bipolar plate of claim 1, wherein a distribution meansis formed in the inflow path in order to give flow resistance to a fluidflowing into the inflow path.
 8. The bipolar plate of claim 7, whereinthe distribution means is formed as a shape having an area correspondedto the section of the inflow path and a certain thickness, and it ismade of a porous material.
 9. A bipolar plate of a fuel cell,comprising: a plate having a certain area and thickness; inflow andoutflow buffer grooves respectively formed at both sides of the plate soas to have a certain area and depth; plural channels for connecting theinflow buffer groove and the outflow buffer groove; plural bufferprotrusions formed in the inflow and outflow buffer grooves so as tohave a certain height; an inflow path formed on the plate so as to beconnected to the inflow buffer groove; and an outflow path formed on theplate so as to be connected to the outflow buffer groove.
 10. Thebipolar plate of claim 9, wherein the buffer protrusions are linearlyarranged between the channels.
 11. The bipolar plate of claim 9, whereinthe buffer protrusions are linearly arranged on the channels.
 12. Thebipolar plate of claim 9, wherein the buffer protrusions are irregularlyarranged.
 13. The bipolar plate of claim 9, wherein the bufferprotrusions have the same height, and the height of the bufferprotrusion is the same with the depth of the inflow buffer groove or theoutflow buffer groove.
 14. The bipolar plate of claim 9, wherein thebuffer protrusion has a rectangular section.
 15. The bipolar plate ofclaim 9, wherein the channels are linearly formed.
 16. The bipolar plateof claim 15, wherein channel width is increased gradually from a channelarranged on the middle to a channel arranged on the edge.
 17. Thebipolar plate of claim 15, wherein width of the channels is uniform, anda projected buffer portion is formed at an inlet side of each channel soas to reduce a width of the inlet.
 18. The bipolar plate of claim 9,wherein the length of the inflow buffer groove and the outflow buffergroove is not less than ⅕ of the length of the channel.
 19. The bipolarplate of claim 9, wherein a distribution means is formed in the inflowpath in order to give flow resistance to a fluid flowing into the inflowpath.
 20. The bipolar plate of claim 19, wherein the distribution meansis formed as a shape having an area corresponded to the section of theinflow path and a certain thickness, and it is made of a porousmaterial.